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white rodgers cycle pilot burner burns for short time and recycles

Larry24
Larry24 Member Posts: 7
I have a Weil McLain boiler (natural gas) with a white rodgers cycle pilot. burner ignites and heats for a short time gas then shuts off and recycles a short time later. What could be causing this?

Comments

  • ddlong1286@yahoo.com
    [email protected] Member Posts: 139
    Check pilot

    Try cleaning the pilot. If it is dirty, it will not produce enought heat to trip the switch if it is dirty. If it is LP, good luck!



    Personally, I would call Weil Mclain and see if you can convert to Hot Surface Ignition, wether it is Nat. or LP(propane). I did that with some Clare furnaces. I wish there was a bounty on cycle pilots, not a good ignition system!



    Don in MO
  • Larry24
    Larry24 Member Posts: 7
    short cycle

    I may have phrased it wrong. The pilot lights the burner ignites and burns for a short time and then goes out. Then after a few minutes the cycle starts all over again.
  • Paul48
    Paul48 Member Posts: 4,470
    ?

    Which Weil Mclain boiler? What controls?
  • Larry24
    Larry24 Member Posts: 7
    edited December 2011
    what controls?

    Hot water boiler, white rodgers cycle pilot,  this internet connection should help: http://www.emersonclimate.com/en-US/products/valves/Documents/0037-5034.pdf
  • Larry24
    Larry24 Member Posts: 7
    what controls?

    Hot water boiler, white rodgers cycle pilot,  this internet connection should help: http://www.emersonclimate.com/en-US/products/valves/Documents/0037-5034.pdf
  • Steamhead
    Steamhead Member Posts: 14,863
    Probably the sensor

    which plugs into the gas valve. These are still available.
    All Steamed Up, Inc.
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
    Consulting
  • Steve Whitbeck
    Steve Whitbeck Member Posts: 669
    mercury switch

    They are still available but are expensive. Just did one two days ago.
  • Larry24
    Larry24 Member Posts: 7
    sensor

    If you are talking about the White rodgers mercury flame sensor, I just installed a brand new one. 
  • ddlong1286@yahoo.com
    [email protected] Member Posts: 139
    Past experiances

    I have seen this ignition system on different gas burners and none of them work well. Any one remember the Carrier Multi-Zone roof top units? I worked on four of them at the local community college. The hoof of the pilot would warp and not direct enough flame to keep the mercury bulb hot enough to keep the main flame on. The cycle was like this:



    Pilot lights, flame heats mercury bulb, switch closes to bring main flame on, main burner lights, burns for anywhere from seconds to minutes then main flame goes off and pilot heats up mercury bulb again to close switch to bring on main burner and keeps cycling like that till your pilot times out(if pilot actually goes off and starts sparking to relight) or thermostat actually satisfies. I have seen this on the aforementioned Multi-Zone, Clare furnaces, & Heat Controller Furnaces. For some reason I have seen the Cycle Pilot on Boilers but they never seemed to have this problem.



    I know that you are not supposed to re-engineer the gas train, but that is what I did with some Clare furnaces when I had to wait for the hot surface ignition re-work kit. Used White Rodgers wonderful(in my opinion) hot surface ignition components that would come in the OEM kit from Clare. Call Weil McLain, see if they have a rework kit so it is OEM(no warranty or liability issues). Other wise I would make my own and not have the continual problem of the Cycle Pilot. You also could install a Honeywell spark ignition kit that converts from standing pilot to spark ignition. Have done that also in the Multi-Zone unit. Worked like a charm.



    If you stay with the cycle pilot system, unless you did this when you changed the sensor, replace the pilot assembly. Like I mentioned above, the hood of the pilot can warp and not direct enough flame to keep the sensor hot. When the main burner comes on, enough heat is lost to the sensor that you loose main flame. Or something else has happened to cause the flame to disrupt and not heat the sensor properly.



    Good luck and let us know how it goes!



    Don in MO
  • Larry24
    Larry24 Member Posts: 7
    Pilot flame

    I adjusted the sensor in the pilot flame and had variable results. First the cycle would not ignite the burner anymore but shut down before burner ignition and recycle. Got it back to getting burner ignition but only for a few seconds of burner burn. Sensor is engulfed in the pilot flame but I still hear a faint clicking sound from the Mercury Flame Sensor even after the burner ignites. Could this simply be a bad sensor control from White Rodgers(since it is brand new)? Has there been any record of this? Or could there be another sensor that could be malfunctioning that is shutting down the burner?
  • Tim McElwain
    Tim McElwain Member Posts: 4,482
    That system

    has a built in pressure switch in the gas valve. It requires 3.5" W.C. pressure or it will not make. If the pilot is good and clean and the tip of the new sensor is glowing cherry red then the mercury pilot system should be okay. That leaves the pressure switch, if it is the problem that requires a new gas valve. If the pressure switch does not close then when the SPDT mercury switch walks over there will be no circuit to keep the pilot valve energized and the system will shut down.
  • ddlong1286@yahoo.com
    [email protected] Member Posts: 139
    What purpose

    Tim, what purpose does the pressure switch serve in the gas valve? I would assume proper gas pressure, anything else? Any other manufacturers use this type of switch in their gas valves?

    Don in MO
  • Steve Whitbeck
    Steve Whitbeck Member Posts: 669
    pressure switch

    The pressure switch on the side of the gas valve keeps the pilot valve open while the mercury switch changes over to main vlalve setting. If the switch goes bad then the pilot will turn on and off constantly. The main valve never comes on. They make a resistor that goes into the circuit to keep the pilot valve open.
  • Tim McElwain
    Tim McElwain Member Posts: 4,482
    The EQSO

    resistor can cause delayed ignitions. I recommend replacement of the gas valve.
  • Tim McElwain
    Tim McElwain Member Posts: 4,482
    White Rodgers was the

    only company to use a pressure switch. It was specifically designed just for the Cycle Pilot System. I would suggest before condeming the valve that you check the inlet and outlet gas pressure to the valve. If it is stable and the valve keeps shutting of then look to replace the valve provided all your voltages are good.
  • Tim McElwain
    Tim McElwain Member Posts: 4,482
    Weil MCLain had a replacement kit for

    some of their boilers to convert from Cycle Pilot to Hot Surface Ignition. That can only be done by the way if it is a factory authorized changeover. HSI is not typically allowed to replace a pilot operated system.
  • Larry24
    Larry24 Member Posts: 7
    Preasure switch

    I want to thank all for their input. When replacing the transformer I had inadvertently  attached the lead from the sensor to the wrong lead on the transformer. It is now burning properly and should be in good running order.
This discussion has been closed.